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Revert "Reduce dbuf_find() lock contention"

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This reverts commit 34dbc618f5.  While this
change resolved the lock contention observed for certain workloads, it
inadventantly reduced the maximum hash inserts/removes per second.  This
appears to be due to the slightly higher acquisition cost of a rwlock vs
a mutex.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
This commit is contained in:
Brian Behlendorf
2022-09-19 11:07:15 -07:00
parent e506a0ce40
commit 223b04d23d
3 changed files with 19 additions and 18 deletions
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include/sys/dbuf.h
+4 -3
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@@ -321,12 +321,13 @@ typedef struct dmu_buf_impl {
uint8_t db_dirtycnt;
} dmu_buf_impl_t;
#define DBUF_RWLOCKS 8192
#define DBUF_HASH_RWLOCK(h, idx) (&(h)->hash_rwlocks[(idx) & (DBUF_RWLOCKS-1)])
/* Note: the dbuf hash table is exposed only for the mdb module */
#define DBUF_MUTEXES 2048
#define DBUF_HASH_MUTEX(h, idx) (&(h)->hash_mutexes[(idx) & (DBUF_MUTEXES-1)])
typedef struct dbuf_hash_table {
uint64_t hash_table_mask;
dmu_buf_impl_t **hash_table;
krwlock_t hash_rwlocks[DBUF_RWLOCKS] ____cacheline_aligned;
kmutex_t hash_mutexes[DBUF_MUTEXES] ____cacheline_aligned;
} dbuf_hash_table_t;
typedef void (*dbuf_prefetch_fn)(void *, uint64_t, uint64_t, boolean_t);